who ever wins this please for your own safety dont do the above!!
tricky one this as is said earlier you have to but the tubes in large ammounts to get exact id (inside dia) but you could get same od(outside dia) then match bore the to ends of tube to same as original tube and weld it in using the correct tig welding wire (insuring not to get too hot) if the area around the weld gets too hot (haz,heat affected zone) the tubes goosed am afraid also you need to have the inside filled with argon also(purge) same as stainless steel.